Wetting Process for the Laundry Inside a Program-Controlled Washing Machine

ABSTRACT

The wetting process for the laundry ( 7 ) inside a program-controlled washing machine, which can be adjusted to the quantity of laundry in a washing drum ( 2 ) which is mounted inside a washing machine tub ( 1 ) in a manner that enables it to rotate about a non-vertical axis ( 3 ) by means of a water supply system ( 8  to  11 ) and a control facility ( 12 ), by means of which the supply of water into the washing machine tub ( 1 ) can be controlled in a temporal manner, and which starts in a first phase (Ph 1 ) with a supply of a first metered quantity of water into the washing machine tub ( 1 ) when the washing drum ( 2 ) is stationary or continuously rotating, is to be optimized with regard to completeness, uniformity and reproducibility. 
     To this end in the first phase (Ph 1 ) the washing drum ( 2 ) rotates at least in an essentially continuous manner with a supply of water until there is at least approximately correspondence between the set and actual quantities of water in the washing machine tub ( 1 ) based on the measurement signals of a water level sensor ( 15 ) and in a second phase (Ph 2 ) rotates in an essentially continuous manner. In this process water is added until the level in the washing machine tub ( 1 ) reaches a water level, which is defined based on the signal pattern of the water level sensor ( 15 ) identified in the first phase (Ph 1 ) in respect of the maximum height and speed of change of the water level (N) and in respect of the dropping back due to subsequent absorption of water by the laundry ( 7 ) or a water level defined during filling and subsequent absorption from the signal pattern of the water level sensor ( 15 ) identified by an expert system within the second phase (Ph 2 ). The number and configuration of individual phases of the wetting process can thus be adjusted in respect of the quantity and specific absorbency of the laundry ( 7 ) to be processed.

The present invention relates to a wetting process for the laundry inside a program-controlled washing machine, which can be adjusted to the quantity of laundry in a washing drum, which is mounted inside a washing machine tub in a manner that enables it to rotate about a non-vertical axis, by means of a water supply system and a control facility, by means of which the supply of water into the washing machine tub can be controlled in a temporal manner and which starts in a first phase with a supply of a first metered quantity of water into the washing machine tub when the washing drum is stationary or continuously rotating.

The invention also relates to a washing machine comprising a washing machine tub with a washing drum, which is mounted in a manner that enables it to rotate about a non-vertical axis, a water supply system and a control facility, by means of which the supply of water into the washing machine tub can be controlled in a temporal manner as well as means for measuring the water level in the washing machine tub.

Such a wetting process and such a washing machine can be found in WO 2004/015187 A1. According to this document a quantity of fresh water adjusted to the determined quantity of laundry inserted is first supplied to a drum, which is driven with rotation speed regulation, of a washing machine with a facility for determining the quantity of laundry inserted dry into the drum and with a regulatable fresh water supply facility and a measurement facility for the supplied quantity of water and with a control facility for influencing the movement pattern of the loaded drum. After a quantity of fresh water that has to be supplied and is a function of absorbency has been reached and determined in the washing machine tub in a first phase the drum is driven in a reversing manner and at intervals in successive phases for a first predetermined period at a rotation speed suitable for washing purposes. The drum is then stopped and/or driven continuously and in one direction at a speed suitable for wetting the laundry for a second period. The required quantity of washing fluid necessary for the subsequent wash phase is only determined, when the drum is driven in a reversing manner and at intervals at a speed suitable for washing purposes after the end of the second predetermined period.

According to WO 2006/018382 A1, which has not been subject to prior publication, a wetting process in a washing machine is divided into the same number of phases as quantity stages are provided for the laundry to be processed. It is therefore possible in any phase of the wetting process to estimate the quantity of washing to be processed, in order to adjust the further progression of the wetting process thereto.

According to DE 41 22 307 A1 water is first supplied to a washing machine up to a certain level with the washing drum stationary and it is observed how the water is absorbed by the laundry. Further water is then added according to the observation while the washing drum is rotating.

When adjusting the quantities of water required for washing purposes in program-controlled washing machines, the wetting processes are to be optimized in particular in such a manner that with every quantity of laundry and every type of textile and the quantity of water in the washing machine tub adjusted thereto the respective batch of laundry is wet in a complete and uniform manner in the shortest possible time, before the actual washing process begins.

Hitherto known wetting phases use a specific predetermined reversing rhythm of the washing drum at reduced drum rotation speed for different quantities of laundry or prefilling of the washing machine tub with the washing drum stationary, followed by continuous rotation of the washing drum in the scooping direction and a subsequent wetting phase as described above or with an additional spin phase to accelerate penetration of the lye into the laundry.

Other wetting phases provide for different sequences with stationary periods of the washing drum, unidirectional or reversing drum movement at low rotation speed and possibly reduced reversing rhythms.

The hitherto known wetting processes have not proven satisfactory in respect of optimum method sequences. In particular the known wetting processes have not really taken due account of different-sized batches of laundry so that in the case of very large batches of laundry (close to the load limit) complete wetting is not achieved, while in the case of small batches of laundry the wetting phase lasts too long in relation to the success of the wetting process. Also the uniformity of wetting is generally unsatisfactory with the known wetting processes.

The object of the present invention is therefore to set up wetting sequences in such a manner that the uniformity of wetting is satisfactory in every batch of laundry and at the same time to adjust wetting processes automatically to the quantity of laundry in a batch of laundry so that the laundry is wet uniformly and with the optimum quantity of water or lye, so that the washing process can be carried out successfully.

According to the invention a wetting process as described in the introduction is configured according to the characterizing part of claim 1 in that in the first phase the washing drum is driven at least in an essentially continuous manner during and after the supply of the first metered quantity of water until the supplied water is absorbed by the laundry and in a second phase is driven at least in an essentially continuous manner and a further quantity of water is added up to a level defined based on the water level pattern identified in the first phase in respect of the maximum height and speed of change of the water level and in respect of the dropping back of the level due to subsequent absorption of water by the laundry, so that the level in the washing machine tub reaches a water level adjusted during and after refilling based on the water level pattern identified in the first phase in respect of the maximum height and speed of change of the water level and in respect of the dropping back of the level due to subsequent absorption by the laundry.

According to the invention a washing machine as described in the introduction is configured according to the characterizing part of claim 6 in that the means for measuring the water level include a time measurement facility for determining the opening period of a supply valve and the control facility is programmed to control a wetting process for laundry in the washing drum in such a manner that in the first phase the washing drum is driven at least in an essentially continuous manner during and after the supply of the first metered quantity of water until the supplied water is absorbed by the laundry and in a second phase is driven at least in an essentially continuous manner and a further quantity of water is added up to a level defined based on the water level pattern identified in the first phase in respect of the maximum height and speed of change of the water level and in respect of the dropping back of the level due to subsequent absorption of water by the laundry, so that the level in the washing machine tub reaches a water level adjusted during and after refilling based on the water level pattern identified in the first phase in respect of the maximum height and speed of change of the water level and in respect of the dropping back of the level due to subsequent absorption by the laundry.

The observation and evaluation of the parameters of the ongoing wetting process provided according to the invention specifically enable the respective steps of the process to be adjusted to the type and quantity of the present batch of laundry.

In a refinement of the invention at least one of the two phases includes at least one segment, in which the washing drum is driven in a reversing manner, without the water level pattern having a direct influence on the control of the water supply. This specifically allows the wetting process to be shortened, because the laundry to be processed is rearranged more quickly in the drum for a time, so that during subsequent continuous rotation in the scooping direction new regions of the batch of laundry are wet by scooped quantities of water. This also improves the uniformity of wetting.

The intensity of wetting is particularly very significant when the continuous rotation direction of the washing drum corresponds to the direction of effectiveness of a scooping facility disposed therein according to an advantageous embodiment.

It is advantageous if the measurement signals defined by the water level pattern during a segment with continuous washing drum rotation and/or during a segment with reversing drum rotation are supplied to an electric filter with algorithms tailored to the wetting process and the water supply is controlled using the output signal of the filter. It can then be decided during this segment from the current situation whether further quantities of water will be required to soak the laundry intensively so that the required supply quantity can be determined and supplied at an early stage.

The segment with continuously rotating washing drum advantageously lasts until the predetermined level has been reached after reabsorption by the laundry. The next phase or the washing process can then be started directly.

To determine that the predetermined level has been reached, means can be provided for measuring the water level, said means containing a time-measurement facility for determining the opening period of a supply valve or a facility for measuring a quantity of fluid for determining the quantity of fluid supplied.

The control facility advantageously has a comparator for the measurement value of the target level for terminating the phase. It can then be decided after comparison with the calculated reference value whether a second or further phase of the wetting process is to follow the first phase due to the size of the batch of laundry. Moreover a stage with reversing drum movement at a freely selectable time of the phase can be assigned to a phase with continuous rotation of the washing drum in any phase.

If according to a further advantageous refinement of the invention the means for measuring the water level during the reversing drum movement and/or the comparator are switched to inactive, appropriate wetting of the batch of laundry can be carried out without further water being supplied, which would turn soaking to over-saturation for the present batch of laundry, which may be too small for so much water in an as yet unidentified manner.

Only in the next segment of wetting by means of unidirectional rotation of the washing drum just in the scooping direction is it again possible to determine from the quantity of water supplied, which is now to be measured, how large the batch of laundry is. A rotation speed of approximately 20 rpm (corresponding to a circumferential speed of around 0.5 m/s) with a given geometry of the washing machine tub/drum system has proven extremely suitable for this purpose.

The reversing drum movement tailored to the structural features of the washing machine tub and/or the washing drum with a rotation speed in the region of 40 rpm (corresponding to a circumferential speed of around 1 m/l) has proven extremely suitable in a corresponding manner (claim 12). Based on these preconditions the two phases of the wetting process together can last between 60 seconds and 4 minutes, resulting overall in a temporally ideally optimized wetting process. The stated times are a function of the size and absorbency of the respective batch of laundry and can be adjusted correspondingly.

The inventive refinement of the washing machine and method steps suited to this refinement are described in more detail below with reference to an exemplary embodiment of a wetting process.

FIG. 1 shows a wetting process for a large batch of laundry based on a diagram and

FIG. 2 shows a schematic illustration of the parts of a washing machine of relevance to the invention, in which washing machine a wetting process according to FIG. 1 is used.

The description of the wetting process illustrated in FIG. 1 required a washing machine at least similar to the one in FIG. 2 with a washing machine tub 1, in which a washing drum 2 is supported and can be driven by the drive motor 14. According to more recent knowledge of ergonomics when dealing with such washing machines the axis of rotation 3 of the washing drum 2 is aligned at a small angle (e.g. 13°) upward away from the horizontal, so that the user of the washing machine has easier access and can see more easily into the inside of the washing drum 2. This arrangement, in conjunction with particularly shaped agitators 4 and scooping facilities 5 for the lye, particularly in the rotation direction of the arrow 16, also achieved a more intensive flow of lye through the laundry 7 and a reduction in what is known as free liquor, which refers to the quantity of lye in the washing machine tub 1, which is not absorbed by the laundry and is located essentially below the lowest point of the washing drum 2 in the washing machine tub. The described wetting process can of course also be advantageously used with conventional designs as well as with such modern designs.

The washing machine also has a lye supply system, comprising a water connection fitting for the domestic water supply system 8, an electrically controllable valve 9 and a supply line 10 to the washing machine tub 1, which can optionally also pass by way of a detergent dispenser facility 11, from which the supplied water can transport portions of detergent into the washing machine tub. The valve 9 can be controlled by a control facility 12 as a function of a program sequence schedule, which can be linked to a time program and/or the achievement of certain measurement values of parameters (lye level, lye temperature, rotation speed of washing drum, etc.) within the washing machine. A lye heating facility 13 is also present in the washing machine tub 1 and can be switched in a similar manner and according to similar criteria by the control facility 12.

A wash program typically starts—as shown in FIG. 1—with the opening of the valve, to bring water from the domestic water supply system 8 into the washing machine tub 1. Here the water is to be brought into intensive contact as quickly as possible with the laundry 7 in the washing drum 2, so that on the one hand the detergent carried with it can deploy its chemical action as quickly as possible and on the other hand so that the heat produced by the heating facility 13 can be transferred to the laundry 7 in the quickest manner possible.

The diagram in FIG. 1 shows the rotation speed n of the washing drum 2, the volume V of the supplied water [ 1/10 liter] and the water level N [mm] in the washing machine tub 1 over the time t. The rotation speed control in particular characterizes the novel wetting process. The supply of water, optionally the supply of detergent and the control of the heating facility 13 are carried out according to the prior art. The overall wetting process stored in the program comprises two phases Ph1 and Ph2, of which the phase Ph2 is masked in or out as required. Should the wetting in phases Ph1 and Ph2 not suffice, a further phase Ph3 is optionally added (see below). The wetting process is followed directly by the washing process W, which continues with a known form of the reversing drum movement with a circumferential speed of around 1.25 m/s.

In the phase Ph1 the drum 2 is set in motion after a sufficient quantity of fluid (e.g. 2 liters of water, optionally plus detergent) has been supplied. The drum 2 is then moved in just one direction (segment A_(D1)), specifically in the direction (arrow 16), in which the scooping facilities 5 on the washing drum 2 act in the required manner. The set rotation speed of the washing drum 2 is set to a value of approximately 20 rpm (corresponding to a circumferential speed of around 0.5 m/s) for the geometrical dimensions of the washing drum, which are selected for domestic purposes but are not given in more detail here. Depending on the respective distribution of the batch of laundry in the washing drum the actual rotation speed however fluctuates about this value. The drum movement is maintained for a period of approximately 30 seconds. It takes approximately 12 seconds for the required initial quantity of supplied water to be present in the washing machine tub 1. The laundry is then already wet with scooped water.

The value of this initial quantity is determined either by measuring the valve opening time, which is a measure of the absolute quantity supplied in the case of an assumed sufficiently uniform specified quantity supplied by the valve 9 or by indirectly measuring the quantity supplied for example by means of a throughflow meter (not shown). To obtain the set lye level N_(1-o) in the washing machine tub (at 121) monitored by a level measurement facility 15, the value for the initial quantity is placed in a relationship such that the quantity absorbed by the batch of laundry 7 results indirectly therefrom. A large batch of laundry absorbs a lot of water, so the initial quantity of supplied water increases more before the set level N₁₋₀ in the washing machine tub 1 is reached than with a smaller batch of laundry. The absorption speed can be measured using the diagram of the water level N and is a measure of the specific absorbency of the type of textile.

In the phase Ph1 the washing drum 2 is driven in a reversing manner after being driven continuously in the scooping direction (arrow 16) for around 20 seconds at a circumferential speed of around 1.0 m/s. The reversing segment A_(R1) allows the batch of laundry to be thoroughly mixed and also gives the laundry the opportunity to be wet further using the water already supplied. This segment A_(R1) can be up to a minute long and contain more intervals than are shown here by just a few intervals within a relatively short time period. The duration of this segment A_(R1) is essentially a function of the selected reversing rhythm, the lye level and machine-related conditions.

After the reversing segment A_(R1) either the wash phase W starts, if the batch of laundry is small and not very absorbent, or the second phase Ph2, if—as shown here—it is a larger batch of laundry, which can absorb a relatively large quantity of water.

The invention uses the described differences in the water level response between batches of laundry of different sizes and different textiles to decide on the basis of said differences whether the wetting process can be terminated at the end of the phase Ph1 (in the case of a small or not very absorbent batch of laundry) or whether it has to be continued in a particular manner. In the case of a small batch of laundry, the initial quantity of supplied water is perhaps only almost completely absorbed (apart from the residue of the free liquor) because all the parts of the batch of laundry come into contact with the supplied water without significant delay and the initial quantity was already sufficient for the small batch of laundry. If the batch of laundry is identified as small in this manner, as can be identified from the fact that the level N drops only to around the height of the volume diagram V towards the end of the phase Ph1, a switch is made immediately to the wash phase W at this point.

If it is ascertained as required in the manner described above that the batch of laundry to be processed is so large that the lye level N reached in this phase Ph1 cannot suffice to wet the laundry completely, a second phase Ph2 of the wetting process is initiated. In the present diagram the level line N has dropped below the volume line V towards the end of the phase Ph1. This means that so much water has been absorbed in the laundry that the level N drops below the level, which would correspond to the volume V supplied, if the water were to stand in the washing machine tub 1 without absorption effects.

This second phase Ph2 now starts, since the first phase has been terminated with continuous rotation, with a first segment A_(D2) and continued continuous drum movement in the one rotation direction 16 with rotation speeds around 20 rpm (corresponding to a circumferential speed of around 0.5 m/s). If required a segment with a reversing phase at approximately 40 rpm (corresponding to a circumferential speed of around 1.0 m/s) (not shown) can be inserted into this segment. Also individual short spin intervals can be embedded in this segment so the newly absorbed fluid flows better through the laundry.

In this segment A_(D2) of the phase PH2 a predetermined quantity of water is supplied. During this segment A_(D2) with continuous washing drum rotation and/or during a later segment A_(R2) with reversing drum rotation within the phase Ph2 signals emitted by the water level sensor 15 can be supplied to a filter, which is contained in the control facility 12 and not shown specifically, with algorithms tailored to the wetting process and control of the water supply can take place using the output signal of the filter. It is then possible to decide from the current situation during this segment whether further quantities of water will be required to soak the laundry intensively, so that the required supply quantity can be determined and supplied at an early stage. Such algorithms take into account volumes of water supplied, water level patterns during individual time segments and in some instance also water levels reached during filling and after supply and reabsorption periods, during which the laundry no longer absorbs (so-called equalization plateaus) and consist of mathematical equations, which are stored in the filter and modify the signal sequences specifically for the processes and devices.

The segment A_(D2), in which the washing drum 2 is driven continuously in a unidirectional manner in the scooping direction 16 at a rotation speed of approximately 20 rpm (corresponding to a circumferential speed of around 0.5 m/s), as in the phase Ph1, can in turn be interrupted by a reversing segment A_(R2) and again serves to allow the batch of laundry to absorb the water gradually (as can be identified by the slowly dropping level N) and to verify the specific and absolute absorbency of the batch of laundry 7, indirectly therefore the type of textile and quantity of laundry. To this end a measurement is taken (at 15) to determine whether the lye level is dropping below a limit value N_(2-u), which serves as a measure of the quantity of laundry assigned to this phase. If the level drops below this value, more water is added during the continuous movement of the washing drum 2, until the level switching value N_(2-O) is reached. The overall quantity of water supplied to reach the switching point N_(2-O) is—as in phase Ph1—a measure of the quantity of laundry and determines whether the transition should now be made (in the case of a medium-sized batch of laundry) directly to the wash process W now or whether a further phase Ph3 of the wetting process should be initiated. The typical value of the overall quantity of water for a medium-sized batch of laundry can for example be around 18 liters.

The two additional bold dot-dash lines at a lower level than the line V at level 50 in the phase Ph2 and the additional dot-dash and double-dot-dash lines N indicate that correspondingly less water has to be added to the washing machine tub for less absorbent or smaller batches of laundry.

The decision to make the transition to the wash phase W however still depends on the specific absorbency of the batch of laundry. If the dropping speed of the level N at the start of the phase Ph2 is slow, the textiles present cannot be wet particularly quickly with water. They are for example multi-layer textiles, those with coated or water-repellent fibers or membranes, which are particularly difficult to wet. If the level N, as described in paragraph 0032, then also drops below the volume line V at the end of the phase Ph2, the decision should be made in favor of a further phase Ph3, in which parts of the phase Ph2 can be repeated.

If the batch of laundry is particularly large however (overall water quantity more than 18 liters) a further phase Ph3 is also initiated. The phase Ph3 can in turn include a segment like the segment A_(R2) in phase Ph2 with reversing drum movements with short rotation speed intervals up to 40 rpm (corresponding to a circumferential speed of around 1.0 m/s) in each direction. Otherwise the phase Ph3 starts again at least with a continuous rotation segment like A_(D2) at only 20 rpm (corresponding to a circumferential speed of around 0.5 m/s) in the scooping direction 16 and may even include switched short spin intervals. Level regulation is again only activated during continuous rotation so that further water can be added during the wetting movement as required, specifically only in the case of significant subsequent absorption. The structure of the movement sequence and its dependencies correspond to the phase Ph2.

In this phase Ph3 a segment is also added, in which the drum 2 is driven continuously in a unidirectional manner at approximately 20 rpm (corresponding to a circumferential speed of around 0.5 m/s), said segment in turn serving to fill up with water. The set lye level N_(3-o) is now the level provided for washing however and no longer serves to determine the quantity of laundry. After a certain period of mixing through in the scooping direction, the wash process starts with the known parameters. The duration of the mixing through process in this continuous rotation segment can be varied from phase to phase; it preferably increases in length as the number of phases increases.

The levels (of the equalization plateaus) in the individual phases should also rise, at least however from the first phase Ph1 to the second phase Ph2. Lye levels rising with the number of phases increase the overall quantity of water for large batches of laundry; this increase is however slight and the laundry can be soaked more intensively more quickly. If a constant level is selected in advanced phases, a particularly efficient scooping performance of the agitators 4 and effective rearrangement of the laundry within the batch of laundry must be ensured for satisfactory soaking.

To optimize the scooping effect it may be expedient to adjust the rotation speed of the drum in the scooping direction 16 as a function of level or load, if soaking is to be intensified and/or accelerated. For program-related reasons it may be more advantageous to include the reversing phases in the continuous rotation phase instead of the series sequence proposed here.

The inventive measures advantageously allow an improvement in the reproducibility of the soaking process and the washing action, because the water is let in at defined times, in defined quantities and in defined conditions. In an angled drum system—as described in the introduction—the adjustment of the water level to the quantities of laundry present can result in a refinement of load-dependent process conditions, particularly for small batches of laundry. Uniform soaking is also improved for large batches of laundry. This generally tends to optimize the required quantities of water, so reduced water consumption should be observed over longer periods due to differentiation. 

1-11. (canceled)
 12. A method for wetting laundry inside a program-controlled washing machine which can be adjusted to the quantity of laundry in a washing drum mounted inside a washing machine tub in a manner that enables the washing drum to rotate about a non-vertical axis, the washing machine including a means of a water supply system and a control facility controlling the supply of water into the washing machine tub in a temporal manner, the method comprising: a first phase in which a supply of a first metered quantity of water is supplied into the washing machine tub when the washing drum is stationary or continuously rotating, the washing drum being driven at least in an essentially continuous manner during and after the supply of the first metered quantity of water until the supplied water is absorbed by the laundry; a second phase in which the washing drum is driven at least in an essentially continuous manner and a further quantity of water is added up to a level defined based on the water level pattern identified in the first phase in respect of the maximum height and speed of change of the water level and in respect of the dropping back of the level due to subsequent absorption of water by the laundry, so that the level in the washing machine tub reaches a water level adjusted during and after refilling based on the water level pattern identified in the first phase in respect of the maximum height and speed of change of the water level and in respect of the dropping back of the level due to subsequent absorption by the laundry.
 13. The method of claim 12, wherein at least one of the first and second phases includes at least one segment, in which the washing drum is driven in a reversing manner, without the water level pattern having a direct influence on the control of the water supply.
 14. The method of claim 13, wherein the measurement signals defined by the water level pattern during a segment with continuous washing drum rotation and/or during a segment with reversing drum rotation are supplied to an electric filter with algorithms tailored to the wetting process and the water supply is controlled using the output signal of the filter.
 15. The method of claim 13, wherein the washing drum is driven continuously in the one of the directions which corresponds to the effectiveness of a scooping facility disposed therein.
 16. The method of claim 13, wherein the segment with continuously rotating washing drum lasts until a predetermined level is reached after reabsorption by the laundry.
 17. A washing machine comprising: a washing machine tub; a washing drum disposed within the tub which can rotate about a non-vertical axis; a water supply system having a supply valve and a control facility controlling the supply of water into the washing machine tub in a temporal manner; a means for measuring the water level in the washing machine tub including a time measurement facility determining the opening period of the supply valve, the control facility being programmed to control a wetting process for the laundry in the washing drum in such a manner that in a first phase the washing drum is driven in an essentially continuous manner during and after the supply of a first metered quantity of water until the supplied water is absorbed by the laundry and in a second phase the washing drum is driven in an essentially continuous manner and a further quantity of water is added up to a defined level based on the water level pattern identified in the first phase in respect of the maximum height and speed of change of the water level and in respect to the dropping back of the level due to subsequent absorption of water by the laundry, the level in the washing machine tub reaching a water level adjusted during and after refilling based on the water level pattern identified in the first phase in respect to the maximum height and speed of change of the water level and in respect to the dropping back of the level due to subsequent absorption by the laundry.
 18. The washing machine as claimed in claim 17, wherein the means for measuring the water level includes a facility for measuring a quantity of fluid for determining the quantity of fluid supplied.
 19. The washing machine as claimed in claim 17, wherein the control facility has a comparator for the measurement value of a target level to terminate the phase.
 20. The washing machine as claimed in claim 19, wherein the means for measuring the water level during the reversing drum movement and/or the comparator are switched to inactive.
 21. The washing machine as claimed in claim 17, wherein the unidirectional drum movement tailored to the structural features of the washing machine tub and/or the washing drum can be executed at a circumferential speed of around 0.5 m/s.
 22. The washing machine as claimed in claim 17, wherein the reversing drum movement tailored to the structural features of the washing machine tub and/or the washing drum can be executed at a circumferential speed of around 1.0 m/s. 